Regeneration of ion exchange resin and recovery of regenerant solution

Abstract

An apparatus and method for regenerating spent ion exchange resin is described. In one method, a fresh regenerant solution comprising sodium ions and chloride ions is prepared, and passed across spent cation exchange resin to regenerate the spent resin. To recover the spent regenerant solution, a regenerant treatment composition is added to the spent solution to form precipitate flocs, which are then separated out of the regenerant solution. The concentration of at least one of the sodium or chloride ions in the regenerant solution can also be adjusted to form fresh regenerant solution which can be reused.

What is claimed is: 
     
       1. A method of regenerating spent cation exchange resin, the method comprising:
 (a) preparing a fresh regenerant solution comprising sodium ions and chloride ions; 
 (b) passing the regenerant solution across spent cation exchange resin to regenerate the spent cation exchange resin, thereby forming fresh cation exchange resin and spent regenerant solution; 
 (c) dispensing a regenerant treatment composition into the spent regenerant solution, the regenerant treatment composition comprising at least one hydroxide component and at least one carbonate component, thereby forming a treated regenerant liquid and precipitate flocs; 
 (d) separating the precipitate flocs from the treated regenerant liquid to form a separated regenerant solution; 
 (e) adjusting the concentration of the chloride ions in the separated regenerant solution to form fresh regenerant solution; and 
 (f) repeating (b) through (e) with the fresh regenerant solution to regenerate additional spent cation exchange resin. 
 
     
     
       2. A method according to  claim 1  comprising, before (b), backwashing the spent cation exchange resin with backwash water to form spent backwash water comprising resin fines. 
     
     
       3. A method according to  claim 2  wherein the spent cation exchange resin is backwashed by passing a stream of water upwardly though the spent cation exchange resin. 
     
     
       4. A method according to  claim 2  comprising removing the spent backwash water and separating the resin fines from the spent backwash water. 
     
     
       5. A method according to  claim 2  comprising, after (b), rinsing the regenerated cation exchange resin with rinse water comprising softened or distilled water. 
     
     
       6. A method according to  claim 1  wherein in (c) the spent regenerant solution includes at least a portion of spent rinse water used to rinse the regenerated cation exchange resin. 
     
     
       7. A method according to  claim 1  wherein (d) comprises passing the treated regenerant liquid through a filtering cloth to separate the precipitate flocs. 
     
     
       8. A method according to  claim 1  wherein (d) comprises centrifuging the treated regenerant liquid to separate the precipitate flocs. 
     
     
       9. A method according to  claim 1  comprising dispensing the regenerant treatment composition into a flowing stream of spent regenerant solution. 
     
     
       10. A method of regenerating spent cation exchange resin, the method comprising:
 (a) backwashing spent cation exchange resin with backwash water to form spent backwash water comprising resin fines; 
 (b) passing fresh regenerant solution comprising sodium ions and chloride ions, across spent cation exchange resin, to form regenerated cation exchange resin and spent regenerant solution; 
 (c) forming a treated regenerant liquid and precipitate flocs by dispensing into the spent regenerant solution, a regenerant treatment composition comprising at least one hydroxide component and at least one carbonate component; 
 (d) separating the treated regenerant liquid from the precipitate flocs; and 
 (e) adjusting the concentration of the chloride ions in the treated regenerant liquid to form fresh regenerant solution. 
 
     
     
       11. A method according to  claim 10  comprising repeating (b) through (e) with batches of the backwashed spent cation exchange resin to form additional regenerated cation exchange resin. 
     
     
       12. A method according to  claim 10  wherein (a) comprises backwashing the spent cation exchange resin by passing water upwardly though the spent cation exchange resin. 
     
     
       13. A method according to  claim 10  wherein (a) further comprises separating the resin fines from the spent backwash water. 
     
     
       14. A method according to  claim 10  comprising, after (b), rinsing the regenerated cation exchange resin with rinse water comprising softened or distilled water. 
     
     
       15. A method according to  claim 10  wherein in (b) the spent regenerant solution includes at least a portion of the spent backwash water used to backwash the regenerated cation exchange resin. 
     
     
       16. A method according to  claim 10  wherein (c) comprises dispensing the regenerant treatment composition into a flowing stream of the spent regenerant solution. 
     
     
       17. A method according to  claim 10  wherein (d) comprises passing treated regenerant liquid through a filtering cloth to separate the precipitate flocs. 
     
     
       18. A method of regenerating spent cation exchange resin, the method comprising:
 (a) backwashing spent cation exchange resin with backwash water passed upwardly though the spent cation exchange resin to form spent backwash water comprising resin fines; 
 (b) separating the resin fines from the spent backwash water and mixing the separated resin fines with the spent cation exchange resin; 
 (c) passing fresh regenerant solution comprising sodium ions and chloride ions, across the spent cation exchange resin and resin fines, to form regenerated cation exchange resin and spent regenerant solution; 
 (d) forming a treated regenerant liquid and precipitate flocs by dispensing into the spent regenerant solution, a regenerant treatment composition comprising at least one hydroxide component and at least one carbonate component; 
 (e) separating the treated regenerant liquid from the precipitate flocs; and 
 (f) adjusting the concentration of the chloride ions in the treated regenerant solution to form fresh regenerant solution. 
 
     
     
       19. A method according to  claim 18  comprising repeating (b) through (f) with batches of the backwashed spent cation exchange resin to form additional regenerated cation exchange resin. 
     
     
       20. A method according to  claim 18  comprising, after (c), rinsing the regenerated cation exchange resin with rinse water comprising softened or distilled water. 
     
     
       21. A method according to  claim 18  wherein (c) comprises dispensing the regenerant treatment composition into a flowing stream of the spent regenerant solution. 
     
     
       22. A method according to  claim 18  wherein (e) comprises passing the treated regenerant liquid through a filtering cloth to separate the precipitate flocs.